Method for Manufacturing High-Purity Erbium, High-Purity Erbium, Sputtering Target Composed of High-Purity Erbium, and Metal Gate Film having High-Purity Erbium as Main Component

ABSTRACT

Provided are a method for manufacturing high-purity erbium, wherein crude erbium oxide is mixed with reducing metal, erbium is reduced and distilled by heating the mixture in a vacuum, and the distillate is melted in an inert atmosphere to obtain high-purity erbium; and high-purity erbium, wherein the purity excluding rare-earth elements and gas components is 4 N or higher and the oxygen content is 200 wtppm or less. An object of this invention is to provide a method of highly purifying erbium, which has a high vapor pressure and is difficult to be refined in a molten metal state, as well as technology for efficiently and stably providing high-purity erbium obtained with the foregoing method, a sputtering target composed of high-purity erbium, and a metal gate film having high-purity erbium as a main component.

TECHNICAL FIELD

The present invention relates to a method of highly purifying erbium,which has a high vapor pressure and is difficult to be refined in amolten metal state, high-purity erbium obtained thereby, a sputteringtarget composed of high-purity erbium, and a metal gate film havinghigh-purity erbium as a main component.

BACKGROUND ART

Erbium (Er) is a rare-earth element, and it is contained in the earth'scrust as a mineral source and as a mixed composite oxide. Althoughrare-earth elements are so called because they are separated fromrelatively rare existing minerals, they are not that rare when viewed inlight of the entire crust. Erbium's atomic number is 68, and it is agray-colored metal having an atomic weight of 167.3 and comprising ahexagonal close-packed structure. Erbium has a melting point of 1530°C., a boiling point of 2860° C., and a density of 9.07 g/cm³. Erbium'ssurface is oxidized in the air, it gradually melts in water, and it issoluble in acid. Erbium has superior corrosion resistance and wearresistance properties, shows high paramagnetic property, and generatesoxides (Er₂O₃) at high temperatures.

With rare-earth elements, it is generally said that compounds with theoxidation number 3 are stable, and erbium is also trivalent. In recentyears, research and development are being promoted for using erbium as ametal gate material or an electronic material for High-k use and thelike, and is a metal that is attracting attention.

Nevertheless, since erbium metal has a problem in that it is easilyoxidized during refining, a high-purity erbium product did not existsince its high purification was difficult.

Moreover, erbium has been used as a magnetic refrigerant material, butsince its use as an electronic component was not considered, it cannotbe said that it was a metal that attracted much attention. Accordingly,there are not many documents relating to practical methods of extractingerbium. Some reference documents are listed below, but they merelydescribe erbium as one of the elements in the extraction of rare-earthmetals.

Disclosed is technology of manufacturing rare-earth elements of Sm, Euand Yb by mixing the oxide powders of Sm, Eu and Yb and the misch metal,making the mixed powder into a briquette, and subjecting it to vacuumthermal reduction using the misch metal as the reductant. The mischmetal is previously subject to hydrogenation treatment to obtain powderymisch metal hydride, and this is mixed and molded into a briquette inorder to prevent the oxidization and combustion during the pulverizationprocess of the misch metal (for example, refer to Patent Document 1). Inthis example, although there is a scheme in the use of misch metal asthe reductant, it does not aim for higher purification, and there is aproblem in that there is a limit in achieving high purification.

Proposed is technology in which halide of the rare-earth metal isreduced with calcium or calcium hydride; and when the obtainedrare-earth metal and the slag are divided, a slag separating jig isplaced in molten slag to solidify the slag and remove the slag togetherwith the jig. Lanthanum, cerium, praseodymium, and neodymium areselected as the rare earths (for example, refer to Patent Document 2).Since this technology is unable to sufficiently eliminate the slag,there is a problem in that it is difficult to achieve high purification.

Proposed is a manufacturing method of rare-earth metals by adding areductant to a fluoride material of rare-earth metal and performingthermal reduction of heating the mixture at high temperature. A mixedcomposition comprising fluorides of rare-earth metals and lithiumfluoride, or a mixed composition added with one or more types of bariumfluoride and calcium fluoride is used as the raw material. In this case,the use of a fused-salt electrolysis bath is proposed, and disclosed isthat the oxygen content will become 1000 ppm thereby (for example, referto Patent Document 3). This technology is based on the use of afused-salt electrolysis bath, and there is a problem in that acomplicated process is required and the effect of oxygen elimination isalso insufficient. There is also the problem of lithium, barium, calciumand so on being included as impurities.

Proposed is technology of mixing a mixed composition of fluoride ofrare-earth metal and lithium fluoride or a mixed composition added withone or more types of barium fluoride and calcium fluoride, andrare-earth metals; and subjecting the mixture to fusion to extract rareearths. Thermally reduced commercial rare earths are used as the rareearths, and for the mixed composition, a fused-salt electrolysis solventbath for manufacturing alloy of rare-earth metals and iron grouptransition metals is used.

Although it is also possible to obtain high-purity rare-earth metals inwhich the oxygen content is 300 ppm or less, and with few impuritiessuch as calcium, lithium and fluorine (for example, refer to PatentDocument 4), this technology is also based on the use of a fused-saltelectrolysis bath and requires a complicated process. In addition, thereis the problem of lithium, barium, calcium and so on being included asimpurities, and effect of oxygen elimination is also insufficient.

Proposed is a refining method for obtaining high-purity rare earths byadding Mg or Zn to rare-earth metals containing Ta as impurities,melting the mixture in a crucible, solidifying this, eliminating theportion highly containing Ta located at the bottom of the crucible, andperforming vacuum distillation to the portion low containing Ta (forexample, refer to Patent Document 5). Nevertheless, since there is aproblem in that the added metal are included as impurities and theelimination of Ta is also insufficient, there is a problem in that thelevel of high purification is low.

As shown in the foregoing documents, the effect of refining erbium isnot necessarily sufficient, and in particular only a handful ofdocuments seek the reduction of oxygen. Among those that do, there is aproblem in that the reduction of oxygen is insufficient. In addition,methods that adopt the fused-salt electrolysis entail a complicatedprocess, and there is a problem in that the refining effect isinsufficient. Like this, the current situation is that there is noefficient and stable manufacturing method to obtain high-purity erbiumthat is a high-melting point metal, has a high vapor pressure, and inwhich refining is difficult in a molten metal state.

[Patent Document 1] Japanese Laid-Open Patent Publication No. S61-9533[Patent Document 2] Japanese Laid-Open Patent Publication No. S63-11628[Patent Document 3] Japanese Laid-Open Patent Publication No. H7-90410[Patent Document 4] Published Japanese Translation No. H7-90411 of PCTApplication[Patent Document 5] Japanese Laid-Open Patent Publication No. H8-85833

SUMMARY OF INVENTION Problems to be Solved by the Invention

An object of this invention is to provide a method of highly purifyingerbium, which has a high melting point and is difficult to be refined ina molten metal state, as well as technology for efficiently and stablyproviding high-purity erbium obtained with the foregoing method, asputtering target composed of high-purity erbium, and a metal gate filmhaving high-purity erbium as a main component.

Means for Solving the Problems

As a result of intense study conducted by the present inventors in orderto achieve the foregoing object; provided is a manufacturing method ofhigh-purity erbium, wherein crude erbium oxide is mixed with reducingmetal, erbium is reduced and distilled to refine the erbium by heatingthe mixture in a vacuum, and the distillate is melted in an inertatmosphere to obtain high-purity erbium. This manufacturing process isthe foundation of the present invention, and, with respect to therespective conditions thereof, the optical conditions may be suitablyselected according to the purity of the raw material and the type ofreducing metal to be used.

Generally speaking, when mixing erbium oxide and reducing metal andheating the mixture to perform the reduction and distillation of erbium,it is desirable to heat the mixture to a temperature of 1500 to 2500° C.in order to efficiently perform the reduction and distillation.Normally, a raw material having a purity of 3 N or less is used, buthigh-purity erbium having a purity of 4 N can be obtained based on therefining in the manufacturing method of high-purity erbium according tothe present invention.

As described in the foregoing conventional technologies, erbium easilybonds with oxygen, and is a material in which oxygen elimination isdifficult. Nevertheless, the present invention is able to obtainhigh-purity erbium, wherein the purity excluding rare-earth elements andgas components is 4 N or higher and the oxygen content is 200 wtppm orless. The foregoing high-purity erbium is a novel material, and iscovered by the present invention.

In addition, by the manufacturing method of high-purity erbium accordingto the present invention; it is possible to achieve that the purityexcluding rare-earth elements and gas components is 4 N or higher,oxygen content is 200 wtppm or less, elements of alkali metals arerespectively 10 wtppm or less, elements of transition metals arerespectively 100 wtppm or less, and radioactive elements arerespectively 10 wtppb or less.

The manufacturing method of high-purity erbium according to the presentinvention covers the foregoing method. In addition, the high-purityerbium obtained as described above is a novel material, and is coveredby the present invention.

The erbium obtained by the foregoing distillation is melted in a vacuumand solidified into an ingot. This ingot can be cut into a prescribedsize and subject to a grinding process in order to form a sputteringtarget.

Accordingly, it is possible to obtain a high-purity erbium sputteringtarget, wherein the purity excluding rare-earth elements and gascomponents is 4 N or higher, oxygen content is 200 wtppm or less,elements of alkali metals are respectively 10 wtppm or less, elements oftransition metals are respectively 100 wtppm or less, and radioactiveelements are respectively 10 wtppb or less.

In addition, by sputtering the foregoing target, it is possible to formon a substrate a metal gate film having high-purity erbium as a maincomponent, wherein the purity excluding rare-earth elements and gascomponents is 4 N or higher, oxygen content is 200 wtppm or less,elements of alkali metals are respectively 10 wtppm or less, elements oftransition metals are respectively 10 wtppm or less, and radioactiveelements are respectively 10 wtppb or less. The foregoing sputteringtarget and metal gate film are also novel materials, and are covered bythe present invention.

EFFECTS OF INVENTION

The present invention yields superior effects of being able to provide amethod of highly purifying erbium, which has a high vapor pressure andis difficult to be refined in a molten metal state, as well asefficiently and stably providing high-purity erbium obtained thereby, asputtering target composed of high-purity erbium, and a metal gate filmhaving high-purity erbium as a main component.

DESCRIPTION OF EMBODIMENTS

The present invention is able to use a raw material of crude erbiumoxide having a purity level of 3 N or lower as the erbium raw materialfor high purification. This raw material contains Na, K, Ca, Mg, Fe, Cr,Ni, O, C, N and so on as primary impurities excluding rare-earthelements.

The crude erbium oxide is mixed with metal with reducing character andthermally reduced in a vacuum at 1500 to 2500° C. Although yttrium (Y)metal having low vapor pressure and high reducing power is effective asthe metal with reducing character, lanthanum (La) and other reducingmetals may also be used. There is no particular limitation on the typeof reducing metal so as long as it has low vapor pressure and highreducing power.

Pursuant to the progress of reduction of erbium oxide, erbium isdistilled and erbium with improved purity is stored in the capacitor.This distillate is melted in a crucible, and solidified into an ingot.The melting and solidification process is preferably performed in aninert atmosphere. It is thereby possible to suppress the rise in oxygencontent. Although it is also possible to perform the melting andsolidification process in a vacuum, since the yield tends to becomeinferior, it is desirable to perform the process in an inert atmosphereas described above. Nevertheless, the present invention is not denyingthe performance of the foregoing process in a vacuum.

It is thereby possible to manufacture high-purity erbium, wherein thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 200 wtppm or less, elements of alkali metalsare respectively 10 wtppm or less, elements of transition metals arerespectively 100 wtppm or less, and radioactive elements arerespectively 10 wtppb or less.

The foregoing alkali metal elements are lithium, sodium, potassium,rubidium, cesium, and francium, and these elements are electricallypositive. For example, if erbium is used for an electronic component,there is a problem in that the elements with a small atomic radius willeasily move within the device, and destabilize the properties of thedevice. As the total amount, inclusion up to 50 wtppm, and preferably upto 10 wtppm is acceptable, but it goes without saying that less thebetter. Thus, content of the respective alkali metal elements is 10wtppm or less, and preferably 1 wtppm or less.

Moreover, the same problems arise with alkaline-earth metal elements,and the content of the respective alkaline-earth metal elements is 20wtppm or less, and preferably 1 wtppm or less.

The foregoing transition metal elements are metals that belong to groups3 to 11 in the periodic table, and representative examples thereof aretitanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper,zinc, and the like. These elements induce the increase of the leakcurrent and cause the deterioration in pressure resistance. As the totalamount, inclusion up to 1000 wtppm, and preferably up to 500 wtppm isacceptable, but less the better. As described above, since thetransition metal elements are individually analyzed and controlled, theamount of inclusion thereof is desirably reduced to 100 wtppm or less,more preferably to 10 wtppm or less, and most preferably to 1 wtppm orless, respectively.

Representative examples of radioactive elements are uranium, actinium,thorium, lead, and bismuth, and the radioactive elements cause a softerror of the accumulated charge in the memory cells becoming inverted.Accordingly, it is necessary to reduce the amounts of such radioactiveelements as well as limit the alpha dose that is generated from suchelements. As the total amount of radioactive elements, the inclusion upto 20 wtppb is acceptable, but should be reduced as much as possible. Asdescribed above, each of the foregoing elements can be individuallyanalyzed and controlled, and, preferably, these elements arerespectively 10 wtppb or less, and more preferably 5 wtppb or less.

As a result of measuring the alpha dose of the target of the presentinvention with a gas-flow proportional counter as the measuring device,the alpha dose was 0.01 cph/cm² or less.

The reason why the rare-earth elements are excluded from the high-purityerbium as described above is because: it is technically difficult toeliminate such rare-earth elements upon manufacturing high-purity erbiumsince the other rare earths themselves have similar chemical propertiesas erbium; and the properties will not be affected significantly sincetheir properties are approximate even if they are included asimpurities.

Under the foregoing circumstances, the inclusion of other rare earths istolerated to a certain degree, but it goes without saying that theinclusion of such other rare earths is reduced as much as possible inorder to improve the properties of the erbium itself.

Moreover, the reason why the purity excluding gas components is 4 N orhigher is because the elimination of gas components is difficult, and,if such gas components are counted, it will no longer be an indicationof the improvement of purity. In addition, it is often the case that theexistence of small amounts of gas components is harmless in comparisonto other impurity elements.

Nevertheless, even in the foregoing cases, in particular, oxygen amongthe gas components is easily incorporated. In cases where the oxygeninclusion exceeds 200 wtppm, if oxygen is incorporated into the targetdescribed later, splashes will occur during the sputtering due to theoxygen, and uniform deposition cannot be performed.

In addition, the existence of oxides is undesirable since it will causethe generation of particles and nodules. Moreover, since it will have nosmall effect on the properties of the metal gate film described later,it goes without saying that it is necessary to reduce oxides as much aspossible. Accordingly, it is desirable to strictly control the oxygencontent as a matter of course. Preferably, the oxygen content is 100wtppm or less, and more preferably 10 wtppm or less.

When forming a thin film of an electronic material such as a gateinsulation film or a thin film for metal gate, such thin film is oftenformed by sputtering, and sputtering is a superior method as a means forforming a thin film. Accordingly, it is effective to use the foregoingerbium ingot to manufacture a high-purity erbium sputtering target.

The target can be manufactured with standard processes such as forging,rolling, machining, and finishing (polishing). In particular, there isno particular limitation in the manufacturing process, and themanufacturing process may be arbitrarily selected.

Based on the above, the present invention provides a high-purity erbiumsputtering target characterized in that the purity excluding rare-earthelements and gas components is 4 N or higher, oxygen content is 200wtppm or less, elements of alkali metals are respectively 10 wtppm orless, elements of transition metals are respectively 100 wtppm or less,and radioactive elements are respectively 10 wtppb or less. Uponmanufacturing the target, the foregoing high-purity erbium ingot is cutinto a prescribed size, and this is machined and polished.

Moreover, by sputtering this high-purity target, high-purity erbium canbe deposited on a substrate. It is thereby possible to form on asubstrate a metal gate film having high-purity erbium as a maincomponent characterized in that the purity excluding rare-earth elementsand gas components is 4 N or higher, oxygen content is 200 wtppm orless, elements of alkali metals are respectively 10 wtppm or less,elements of transition metals are respectively 100 wtppm or less, andradioactive elements are respectively 10 wtppb or less. The compositionof the target is reflected in the film on the substrate, and ahigh-purity erbium film can thereby be formed.

Although the metal gate film may sustain the uniform composition withthe foregoing high-purity erbium, it may also be formed as mixture,alloy or compound with other gate materials. This can be achieved by thesimultaneous sputtering with the target of other gate materials orsputtering using a mosaic target. The present invention also covers theforegoing aspects. Although the impurity content will change dependingon the impurity content in the raw material, the respective impuritiescan be adjusted to be within the foregoing range by adopting the methoddescribed above.

The present invention provides a method of highly purifying erbium; andtechnology capable of efficiently and stably providing high-purityerbium based on the foregoing method, a sputtering target composed ofhigh-purity material erbium, and a thin film for metal gate havinghigh-purity erbium as main component.

EXAMPLES

The present invention is now explained in detail with reference to theExamples. These Examples are merely illustrative, and the presentinvention shall in no way be limited thereby. In other words, variousmodifications and other embodiments based on the technical spiritclaimed in the claims shall be included in the present invention as amatter of course.

Example 1

As the erbium raw material, crude erbium oxide (Er₂O₃) of 3 N was used.The impurities contained in this raw material are shown in Table 1.

Subsequently, the erbium raw material was mixed with yttrium (Y) as thereducing metal, and a vacuum distillation apparatus was used tothermally reduce the mixture in a vacuum at 1600° C. Pursuant to theprogress of reduction of erbium oxide, erbium was distilled to improvethe purity, and the erbium with improved purity was stored in acapacitor.

Distillation and thermal reduction reaction was as follows:

Er₂O₃ (solid)+2Y (solid)→2Er (gas) +3Y₂O₃ (solid)

10 kg of erbium was extracted from the erbium distillate stored in thecapacitor, a CaO crucible was used to melt the extracted erbium in Aratmosphere, and this was solidified into an ingot.

It was thereby possible to manufacture high-purity erbium in which thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 40 wtppm or less, elements of alkali metalsare respectively 1 wtppm or less, elements of transition metals arerespectively 20 wtppm or less, and radioactive elements are respectively5 wtppb or less. The results are also shown in Table 1.

As a result of measuring the alpha dose of the target with a gas-flowproportional counter as the measuring device, the alpha dose was 0.01cph/cm² or less.

The sputtering target obtained from the foregoing ingot was also able toretain a high purity level, and it was possible to form a high-purityerbium thin film with uniform characteristics on a substrate bysputtering the foregoing sputtering target.

TABLE 1 Alkaline- Alkali earth Radioactive metals metals Transitionmetals Gas components elements Elements Na K Ca Mg Fe Cr Ni O C N U ThRaw material 150 20 120 80 1600 100 300 — 1000 1 wt % 1000 5000 Example1 0.2 <0.1 0.5 0.8 16 6.5 0.5 40 20 <10 <5 <5 Example 2 0.6 0.3 <0.1 0.77 1.4 0.7 60 70 20 6 8 Example 3 10 1.0 13 4.5 100 20 30 200 50 60 <5 <5Example 4 <0.1 <0.1 <0.1 <0.1 0.3 0.1 0.1 <10 <10 <10 <5 <5 Example 53.5 0.7 6 2 43 13 21 120 30 20 <5 <5 (Excluding the indication “wt %”for the raw material, unit of others is wtppm; provided that the unit iswtppb for U and Th)

Example 2

The same raw material as Example 1 was used to perform reduction. Theentire process was performed as with Example 1 other than that La wasused as the reductant.

It was thereby possible to manufacture high-purity erbium in which thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 60 wtppm or less, elements of alkali metalsare respectively 1 wtppm or less, elements of transition metals arerespectively 10 wtppm or less, and radioactive elements are respectively10 wtppb or less. Although both Example 1 and Example 2 were able toachieve an oxygen content of 100 wtppm or less, in the case of Example2, the content of radioactive elements U and Th was slightly high.

The sputtering target obtained from the foregoing ingot was also able toretain a high purity level, and it was possible to form a high-purityerbium thin film with uniform characteristics on a substrate bysputtering the foregoing sputtering target. The results are also shownin Table 1.

Example 3

The entire process was performed as with Example 1 other than thaterbium oxide of 3 N level was used as the raw material and thereduction/distillation temperature was set to 2500° C.

It was thereby possible to manufacture high-purity erbium in which thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 200 wtppm or less, elements of alkali metalsare respectively 10 wtppm or less, elements of transition metals arerespectively 100 wtppm or less, and radioactive elements arerespectively 5 wtppb or less. In this Example, the impurity content washigh overall since the reduction/distillation temperature was high, butit was still possible to keep it within an acceptable range.

The sputtering target obtained from the foregoing ingot was also able toretain a high purity level, and it was possible to form a high-purityerbium thin film with uniform characteristics on a substrate bysputtering the foregoing sputtering target. The results are also shownin Table 1.

Example 4

The metal erbium obtained in Example 1 was subject to distillation onceagain to manufacture metal erbium. The impurity content thereof is shownin Table 1.

It was thereby possible to manufacture high-purity erbium in which thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 10 wtppm or less, elements of alkali metalsare respectively 1 wtppm or less, elements of transition metals arerespectively 1 wtppm or less, and radioactive elements are respectively5 wtppb or less. In this Example, results of an extremely low impurityconcentration were obtained due to the effect of redistillation.

The sputtering target obtained from the foregoing ingot was also able toretain an even higher purity level as shown in Table 1, and it waspossible to form a high-purity erbium thin film with uniformcharacteristics on a substrate by sputtering the foregoing sputteringtarget.

Example 5

The entire process was performed as with Example 1 other than thaterbium oxide of 3 N level was used as the raw material and thereduction/distillation temperature was set to 2000° C.

It was thereby possible to manufacture high-purity erbium in which thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 200 wtppm or less, elements of alkali metalsare respectively 10 wtppm or less, elements of transition metals arerespectively 100 wtppm or less, and radioactive elements arerespectively 5 wtppb or less. In this Example, the impurity content wasof medium level between Example 1 and Example 3 since thereduction/distillation temperature was set in the middle of thoseExamples.

The sputtering target obtained from the foregoing ingot was also able toretain a high purity level, and it was possible to form a high-purityerbium thin film with uniform characteristics on a substrate bysputtering the foregoing sputtering target. The results are also shownin Table 1.

Comparative Example 1

The same raw material as Example 1 was used and Ca was used as thereductant, but it was not possible to perform the reduction. This isbecause Ca was unable to function as a reductant.

Comprehensive Evaluation of Results of Examples

Although not specifically illustrated in the foregoing Examples, it wasconfirmed that the intended results can be obtained if the temperatureupon performing the reduction and distillation of erbium is within therange of 1500 to 2500° C.

Moreover, although not specifically illustrated in the Examples, when ahigh-purity raw material having a purity exceeding 3 N was used, it wasconfirmed that high-purity erbium having a purity of 4 N, wherein thepurity excluding rare-earth elements and gas components is 4 N orhigher, oxygen content is 200 wtppm or less, elements of alkali metalsare respectively 10 wtppm or less, elements of transition metals arerespectively 100 wtppm or less, and radioactive elements arerespectively 10 wtppb or less, could be obtained under the refiningconditions of the present invention. It was particularly confirmed thatoxygen content of 200 wtppm or less can be achieved

The foregoing high-purity erbium is able to sustain its purity even whenprocessed into a target; and a high-purity erbium sputtering target, inwhich the purity excluding rare-earth elements and gas components is 4 Nor higher, oxygen content is 200 wtppm or less, elements of alkalimetals are respectively 10 wtppm or less, elements of transition metalsare respectively 100 wtppm or less, and radioactive elements arerespectively 10 wtppb or less, was obtained.

In addition, even when the foregoing high-purity erbium was deposited ona substrate by sputtering, the purity of the target was reflected in thefilm, and it was confirmed that metal gate film having high-purityerbium as a main component, wherein the purity excluding rare-earthelements and gas components is 4 N or higher, oxygen content is 200wtppm or less, elements of alkali metals are respectively 10 wtppm orless, elements of transition metals are respectively 100 wtppm or less,and radioactive elements are respectively 10 wtppb or less, can beobtained.

The foregoing is not indicated in the Examples in order to avoidrepetition and complication, but was confirmed as specific conditions.

INDUSTRIAL APPLICABILITY

The manufacturing method of high-purity erbium according to the presentinvention can resolve the problems encountered in conventional methods;namely, that erbium has a high melting point and vapor pressure and isdifficult to be refined in a molten metal state; and facilitates thehigh purification of erbium. The present invention yields superioreffects in being able to provide the specific method thereof, as well astechnology for efficiently and stably providing high-purity erbiumobtained with the foregoing method, a sputtering target composed ofhigh-purity erbium, and a metal gate film having high-purity erbium as amain component. In particular, the present invention is useful asmaterials of a gate insulation film or a thin film for metal gate sincethey will not, as electronic materials to be disposed in the vicinity ofthe silicon substrate, deteriorate or disturb the functions ofelectronic devices.

1. A method for manufacturing high-purity erbium, wherein erbium oxideis mixed with reducing metal, the mixture is thereafter heated in avacuum and distilled while being reduced to metal erbium, and thedistillate is melted in an inert atmosphere to obtain high-purity erbiumin which the purity excluding rare-earth elements and gas components is4 N or higher, oxygen content is 200 wtppm or less, elements of alkalimetals are respectively 10 wtppm or less, elements of transition metalsare respectively 100 wtppm or less, and radioactive elements arerespectively 10 wtppb or less.
 2. The method for manufacturinghigh-purity erbium according to claim 1, wherein the mixture is heatedto a temperature of 1500 to 2500° C. during the reduction anddistillation of erbium.
 3. The method for manufacturing high-purityerbium according to claim 2, wherein erbium oxide having a purity of 3 Nor less is used as the raw material, and this is refined to obtainhigh-purity erbium having a purity of 4 N or higher.
 4. (canceled) 5.High-purity erbium, wherein the purity excluding rare-earth elements andgas components is 4 N or higher, oxygen content is 200 wtppm or less,elements of alkali metals are respectively 10 wtppm or less, elements oftransition metals are respectively 100 wtppm or less, and radioactiveelements are respectively 10 wtppb or less.
 6. (canceled)
 7. Ahigh-purity erbium sputtering target made of the high-purity erbiumaccording to claim
 5. 8. A metal gate film having high-purity erbium asa main component, made of the high-purity erbium according to claim 5.9. The high-purity erbium according to claim 5, wherein the alpha doseof the high-purity erbium is 0.01 cph/cm² or less.
 10. A high-purityerbium sputtering target made of the high-purity erbium according toclaim
 9. 11. A metal gate film having high-purity erbium as a maincomponent, made of the high-purity erbium according to claim
 9. 12. Themethod for manufacturing high-purity erbium according to claim 3,wherein the alpha dose of the high purity erbium is 0.01 cph/cm² orless.
 13. The method for manufacturing high-purity erbium according toclaim 1, wherein erbium oxide having a purity of 3 N or less is used asthe raw material, and this is refined to obtain high-purity erbiumhaving a purity of 4 N or higher.
 14. The method for manufacturinghigh-purity erbium according to claim 1, wherein the alpha dose of thehigh purity erbium is 0.01 cph/cm² or less.